Hydraulic fracturing (sometimes called fracking) can be used for recovering oil and natural gas from the ground. Fracking can be performed in vertical wells and in horizontal drilling. In horizontal drilling, a drillhole can be created as a lateral that extends parallel with the rock (e.g. shale) maintaining the substance to be extracted (e.g., oil or natural gas). A hydraulic fracture is formed by pumping, for example, a fracturing fluid under pressure. The pressure may cause the rock formation to crack, allowing the fracturing fluid to enter and extend the crack farther into the formation. A solid proppant (e.g. sand or ceramic) may be added to the fracture fluid after the injection stops to keep the fracture open. The propped fracture becomes a permeable conduit through which formation fluids can flow to the well.
Some claim that fracking may result in contamination of ground and drinking water. Although disputed by the oil and gas industry, a concern remains that fracking has an environmental impact on water used and consumed by the public. Some States are passing legislation placing presumed responsibility on oil and gas producers for water contamination near their wells until they can prove otherwise. Current water testing is performed at small, individual laboratories serving local communities.